Why is the Parker Photo voltaic Probe making an attempt to ‘contact’ the solar?

A 2018 artist’s idea exhibits the Parker Photo voltaic Probe flying into the solar’s outer ambiance, known as the corona, on a mission to assist scientists study extra in regards to the star.
| Photograph Credit score: NASA

Among the many varied locations people have aspired to go to within the photo voltaic system, the solar stays probably the most foreboding. On December 24, 2024, NASA’s Parker Photo voltaic Probe arrived inside 6.1 million km from the star’s floor. This can be a brief distance to be from the solar: no spacecraft has ever made such an in depth strategy. Even the Parker Photo voltaic Probe took seven years to get right here.

The probe made one other strategy to the solar on March 22 and can accomplish that once more on June 19 this yr.

Watching the solar

Daylight is the principle supply of vitality for earthlife. The solar’s core produces this vitality utilizing nuclear fusion. The star additionally has robust, dynamic magnetic fields crisscrossing its floor, and sudden modifications in the best way they’re organized give rise to intense explosions known as photo voltaic flares. Quite a few electrons, protons, and heavy nuclei are spit out of the photo voltaic corona — the uppermost layer of the solar’s ambiance — at about 900 km/s.

These particles carry an infinite quantity of vitality and generally rush in direction of the earth at large pace in an occasion known as a coronal mass ejection. Their results on the earth represent a photo voltaic storm, together with electrical grid failures, lack of telecommunication channels, and harm to the ozone layer. They’ll additionally harm devices onboard satellites.

To know the dynamics of the corona over time and their results on the photo voltaic system at massive, scientists want to look at the solar intently. That is additionally why the Indian Area Analysis Organisation launched and is at the moment working the Aditya-L1 probe, stationed at about 150 million km from the star.

An in a position warmth defend

Round six many years in the past, a scientist named Eugene Parker predicted the existence of the photo voltaic wind: a stream of charged particles flowing out from the solar in all instructions. NASA named the Parker Photo voltaic Probe in his honour.

The probe was launched on board a Delta IV rocket from Cape Canaveral in Florida in August 2018. As soon as in house, the probe’s most pace was an astounding 692,000 km/hr.

To guard in opposition to the solar’s intense warmth, the probe has an 8-foot-wide, 4.5-inch thick carbon-carbon composite materials defend that may stand up to as much as 1,370º C whereas weighing solely 73 kg. This defend was constructed by researchers on the Johns Hopkins Utilized Physics Laboratory. It consists of a carbon composite foam sandwiched between two carbon plates. Its sun-facing aspect is coated with white ceramic paint to mirror as a lot daylight as attainable as a substitute of absorbing it.

Only a few metres behind the defend, in its shadow, the ambient temperature drops to 29º C, permitting the probe’s scientific devices to function with out particular provisions to take care of the temperature. The probe additionally has two units of solar energy arrays: one within the defend’s shadow that provides energy to the devices and the opposite on the sun-facing aspect, which makes use of a particular fluid pump to chill itself whereas powering the probe throughout its shut approaches.

Touching the solar

Curiously, the primary impediment to the mission’s success wasn’t the solar’s warmth however its gravity. Because the probe flew by house at a really excessive pace, it needed to decelerate considerably because it acquired near the solar. If it didn’t, the solar’s gravity would have inspired it to dive proper into the star. That is why Parker’s first mission profile had the probe fly in direction of Jupiter and swing across the gasoline big to realize an optimum pace to fly in direction of the solar. This concept fell out of favour due to the massive journey distance.

The probe’s ultimate mission profile was extra direct: to make use of the mixed gravitational forces of the earth and Venus to slowly spiral nearer to the solar’s floor, within the course of spending greater than 2,000 hours flying by the corona and 24 occasions alongside the photo voltaic equator.

The probe has 4 scientific devices: FIELDS, Built-in Science Investigation of the Solar (ISoIS), Broad-Subject Imager (WISPR), and Photo voltaic Wind Electrons Alphas and Protons (SWEAP). FIELDS measures the electrical and magnetic fields of the solar’s ambiance; ISoIS observes the energetic particles that trigger photo voltaic storms whereas SWEAP information their properties; and WISPR takes photos because it passes by the corona.

A ‘sun-touching’ occasion occurred in April 2021 when Parker moved nearer to the solar than its Alfvén floor — the peak past which the photo voltaic wind can’t have an effect on the star’s floor — as ascertained by the FIELDS and SWEAP devices.

A fifth instrument, known as a Faraday cup, lies exterior the shadow of the warmth defend and measures the density of ions and electrons within the photo voltaic wind. It’s fabricated from a molybdenum alloy with a melting level of two,349º C.

Blowin’ within the (photo voltaic) wind

Parker knowledge has already revealed many new particulars in regards to the solar. The photo voltaic system is ceaselessly coated in mud particles created when house rocks climate and scientists believed the mud should be in every single place. But Parker revealed dust-free pockets close to the solar. The probe additionally detected magnetic switchbacks: components of the photo voltaic wind the place the magnetic subject (created by the collective of charged particles) abruptly bent again on itself.

An vital open query in photo voltaic astrophysics is why the solar’s floor is just 6,000º C or so whereas the photo voltaic corona is 200-times hotter. Primarily based on Parker’s knowledge of magnetic switchbacks and different associated phenomena, scientists imagine the reply to the thriller lies in Alfvén waves: an oscillation of ions within the plasma launched by the solar, set in movement by forces within the surrounding magnetic subject.

Throughout its close-approach on March 22, the Parker Photo voltaic Probe as soon as once more tried to get inside round 6 million km of the solar’s floor. What did it discover this time?

Shamim Haque Mondal is a researcher within the Physics Division, State Forensic Science Laboratory, Kolkata.